* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #6366f1;
    --primary-hover: #4f46e5;
    --bg-color: #f8fafc;
    --card-bg: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --completed-color: #94a3b8;
    --danger-color: #ef4444;
    --danger-hover: #dc2626;
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: 20px;
    color: var(--text-primary);
}

.container {
    max-width: 600px;
    margin: 0 auto;
    background: var(--card-bg);
    border-radius: 16px;
    box-shadow: var(--shadow-lg);
    overflow: hidden;
}

header {
    padding: 24px 20px;
    background: linear-gradient(135deg, var(--primary-color) 0%, #8b5cf6 100%);
    color: white;
    text-align: center;
}

header h1 {
    font-size: 28px;
    font-weight: 700;
    margin-bottom: 8px;
}

.stats {
    font-size: 14px;
    opacity: 0.9;
}

.input-section {
    display: flex;
    gap: 8px;
    padding: 20px;
    border-bottom: 1px solid var(--border-color);
}

#todo-input {
    flex: 1;
    padding: 14px 16px;
    border: 2px solid var(--border-color);
    border-radius: 12px;
    font-size: 16px;
    transition: all 0.2s;
    outline: none;
}

#todo-input:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

#add-btn {
    width: 48px;
    height: 48px;
    border: none;
    background: var(--primary-color);
    color: white;
    border-radius: 12px;
    font-size: 24px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

#add-btn:hover {
    background: var(--primary-hover);
    transform: scale(1.05);
}

#add-btn:active {
    transform: scale(0.95);
}

.filter-section {
    display: flex;
    gap: 8px;
    padding: 16px 20px;
    border-bottom: 1px solid var(--border-color);
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
}

.filter-btn {
    padding: 8px 16px;
    border: 2px solid var(--border-color);
    background: white;
    border-radius: 8px;
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    white-space: nowrap;
    color: var(--text-secondary);
}

.filter-btn:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
}

.filter-btn.active {
    background: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
}

.todo-list {
    list-style: none;
    max-height: 60vh;
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
}

.todo-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 16px 20px;
    border-bottom: 1px solid var(--border-color);
    transition: background 0.2s;
    animation: slideIn 0.3s ease-out;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateX(-10px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.todo-item:hover {
    background: var(--bg-color);
}

.todo-item.completed {
    opacity: 0.6;
}

.todo-checkbox {
    width: 24px;
    height: 24px;
    border: 2px solid var(--border-color);
    border-radius: 6px;
    cursor: pointer;
    position: relative;
    flex-shrink: 0;
    transition: all 0.2s;
    appearance: none;
    -webkit-appearance: none;
}

.todo-checkbox:checked {
    background: var(--primary-color);
    border-color: var(--primary-color);
}

.todo-checkbox:checked::after {
    content: '✓';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    color: white;
    font-size: 16px;
    font-weight: bold;
}

.todo-text {
    flex: 1;
    font-size: 16px;
    line-height: 1.5;
    word-break: break-word;
    color: var(--text-primary);
}

.todo-item.completed .todo-text {
    text-decoration: line-through;
    color: var(--completed-color);
}

.todo-delete {
    width: 32px;
    height: 32px;
    border: none;
    background: transparent;
    color: var(--danger-color);
    font-size: 20px;
    cursor: pointer;
    border-radius: 6px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
    flex-shrink: 0;
    opacity: 0.6;
}

.todo-item:hover .todo-delete {
    opacity: 1;
}

.todo-delete:hover {
    background: rgba(239, 68, 68, 0.1);
    transform: scale(1.1);
}

.todo-delete:active {
    transform: scale(0.9);
}

.footer-actions {
    padding: 16px 20px;
    border-top: 1px solid var(--border-color);
}

.clear-btn {
    width: 100%;
    padding: 12px;
    border: 2px solid var(--border-color);
    background: white;
    border-radius: 8px;
    font-size: 14px;
    font-weight: 500;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all 0.2s;
}

.clear-btn:hover {
    border-color: var(--danger-color);
    color: var(--danger-color);
    background: rgba(239, 68, 68, 0.05);
}

.empty-state {
    padding: 60px 20px;
    text-align: center;
    color: var(--text-secondary);
}

.empty-state-icon {
    font-size: 64px;
    margin-bottom: 16px;
    opacity: 0.5;
}

.empty-state-text {
    font-size: 16px;
}

/* Мобильные устройства */
@media (max-width: 640px) {
    body {
        padding: 12px;
    }

    header h1 {
        font-size: 24px;
    }

    .input-section {
        padding: 16px;
    }

    #todo-input {
        font-size: 16px; /* Предотвращает зум на iOS */
    }

    .todo-item {
        padding: 14px 16px;
    }

    .todo-text {
        font-size: 15px;
    }
}

/* Темная тема (опционально, можно добавить переключатель) */
@media (prefers-color-scheme: dark) {
    :root {
        --bg-color: #0f172a;
        --card-bg: #1e293b;
        --text-primary: #f1f5f9;
        --text-secondary: #94a3b8;
        --border-color: #334155;
    }

    body {
        background: linear-gradient(135deg, #1e293b 0%, #334155 100%);
    }

    #todo-input {
        background: var(--card-bg);
        color: var(--text-primary);
    }

    .filter-btn {
        background: var(--card-bg);
        color: var(--text-secondary);
    }

    .clear-btn {
        background: var(--card-bg);
        color: var(--text-secondary);
    }
}